This section sets a context for two case studies that are described in detail in subsequent sections. First, we will briefly define low level radioactive waste (LLRW). Then we discuss the legislation that mandated construction of a dozen or more regional LLRW disposal facilities in the United States. Finally, we will reflect briefly on how the capability of GIS to integrate multiple data "layers" is useful for siting problems like the ones posed by LLRW. As you read, keep in mind that, although finding sites for LLRW is a special application for GIS in many ways (due to the controversies that surround nuclear power and concerns over public and individual safety), the methods outlined below are equally applicable to any situation in which a location for an facility or an activity needs to be picked with multiple (perhaps conflicting) criteria taken into account (e.g., locating an airport, a highway, a shopping mall, or a park).